Integrated versus separate reading of F-18 FDG-PET/CT and MRI for abdominal malignancies: effect on staging outcomes and diagnostic confidence

Objective Abdominal cancer patients increasingly undergo multimodality imaging. This study evaluates effects of integrated reading of PET/CT and abdominal MRI on staging outcomes and diagnostic confidence compared to "routine" separate reading.

Methods In total, N=201 patients who underwent abdominal MRI and whole-body F-18 FDG-PET/CT within 14 days were retrospectively analyzed. Original MRI and PET/CT reports were retrieved and reported findings translated into a 5-point confidence score (1=definitely benign to 5=definitely malignant) for 7 standardized regions (primary tumor/regional lymph nodes/distant lymph nodes/liver/lung/bone/peritoneum) per patient. Two-reader teams (radiologist + nuclear medicine physician) then performed integrated reading of the images using the same scoring system.

Results Integrated reading led to discrepant findings in 59 of 201 (29%) of patients, with potential clinical impact in 25 of 201 (12%). Equivocal scores decreased from 5.7% (PET/CT) and 5.4% (MRI) to 3.2% (p=0.05 and p=0.14). Compared to the original PET/CT reports, integrated reading led to increased diagnostic confidence in 8.9% versus decreased confidence in 6.6% (p=0.26). Compared with the original MRI reports, an increase in confidence occurred in 9.6% versus a decrease in 6.9% (p=0.18). The effect on diagnostic confidence was most pronounced in lymph nodes (p=0.08 vs. MRI), cervical cancer (p=0.03 vs. MRI), and recurrent disease staging (p=0.06 vs. PET/CT).

Conclusions Integrated PET/CT+MRI reading alters staging outcomes in a substantial proportion of cases with potential clinical impact in 1 out of 9 patients. It can also have a small positive effect on diagnostic confidence, particularly in lymph nodes and cervical cancer, and in post-treatment settings. These findings support further collaboration between radiology and nuclear medicine disciplines.